Pop songwriter David Foster nearly upstaged his friend Chau-Giang Thi Nguyen at Lincoln Center’s Kaplan Hall Monday night. Chau-Giang (Cho-San), who started her musical career at age 6 entertaining Vietnamese soldiers, is the girlfriend of “Robin Hood” producer Brian Grazer, who hosted the evening in absentia because he wasn’t feeling well enough to fly from LA. After Chau-Giang, in Valentino gown, drew ovations playing the piano, she asked Foster to perform for 100 guests who were tucking into filet mignon. Foster — who’s written songs for everyone from Whitney Houston to Andrea Bocelli — played a medley with a running commentary on how his hits had financed his three divorces. He introduced one tune by saying, “This one got my second wife her house in Malibu.” Joining in the laughter were Vivi Nevo, Vera Wang, June Haynes and producer Bill Diggins, whose “What Chilli Wants” was just renewed on VH1.